Circuit card connector



P. E BEAULIEU 1 13 1 CIRCUIT CARD CONNECTOR Oct. 27, 1970 2 Sheets-Sheefl 1 Filed June 17", 1968 1 .B. 2 G 1 F m a w m 7 T7 4 .310 12 1 1 v1 1 W\\\\\\\\ 1 M)! mu FIG.2A- 2711' INVENTOR PHILIP'E. BEAULIEU M% ATTORNEY P. E. BEAULIEU ,0 CIRCUIT CARD CONNECTOR I Filed June l7,' 1968 United States Patent Olfice 3,537,063 Patented Oct. 27, 1970 3,537,063 CIRCUIT CARD CONNECTOR Philip E. Beaulieu, South Burlington, Vt., assignor to International Business Machines Corporation, Armonk, N.Y., a corporation of New York Filed June 17, 1968, Ser. No. 737,403 Int. Cl. H01r 13/62 U.S. Cl. 339-74 8 Claims ABSTRACT OF THE DISCLOSURE A circuit card connector having characteristics suitable for use in closely packed arrays with high speed computer circuitry, without requiring heavy structural supports, is obtained in a connector having the disclosed configuration. The connector is a normally closed, zero or low insertion force, circuit card connector with a spring contact. It has a means (e.g. a cam) operatively engaging the spring contact for applying a force substantially normal to, and substantially through and away from, the point of contact of the spring contact with the circuit card. The distance between active elements on the circuit card and the terminal of the spring contact is minimized. Forces external to the connector and requiring structural support are also minimized.

FIELD OF THE INVENTION This invention relates to a normally closed circuit card connector. More particularly, it relates to such a circuit card connector which is especially suitable for use with high speed computer circuitry.

DESCRIPTION OF THE PRIOR ART Normally closed, zero insertion force connectors are known in the art. For example, U.S. Pat. 3,070,771 discloses a connector suitable for making electrical contact between two printed tape cables. It is cam actuated and has zero insertion force. However, the design as therein disclosed does not include either the feature of minimum distance between active elements on the printed tape and a contact terminal, nor does it minimize forces transmitted to the housing during operation of the connector. Such a connector design would be unsuitable for most high speed computer applications.

U.S. Pat. 3,366,916 to Oktay, assigned to IBM, discloses a zero insertion force circuit card connector design. This design is suitable for some computer uses, but the expandable pressure tubing used there to bias the contacts to their open position is located between the point of contact on the circuit card and the terminal of the contacts. For this reason, the design cannot incorporate a minimum distance feature between active elements on the circuit card and the contact terminals, and the design is unsuited for applications where speed is a critical parameter. The Oktay patent also discloses a connector design wherein the expandable pressure tubing used to bias the contacts to the open position is not located between the contact point and the contact terminal. However, that design is not suited for use with circuit cards.

Since the expandable pressure tubing in both of the Oktay designs is placed between opposing contacts, it increases the spacing between the opposing contacts. This causes a lower capacitance between the contacts, thus increasing impedance between them, which causes noise, resulting in lower effective output signals transmitted through the contacts.

An example of a normally open connector (i.e. a connector in which the spring tension biases the contacts open and in which a force must be applied to the contacts in order to keep them in the closed position) suitable for some computer applications is disclosed in the IBM T echnical Disclosure Bulletin, April 1968, page 1695. However, the design therein disclosed requires considerable bulk in the structural supports because it is of the normally open type, and also because the force to close the contacts is applied at a point close to their supporting base. For these reasons, a heavy steel supporting plate is required for an array containing 50 to of these connectors. The bulk of such a plate adds distance between active elements on the circuit card and the contact terminals. The feature of minimum distance between active elements on a circuit card and the contact terminals therefore cannot be obtained with this design.

While the circuit card connector art is a highly sophisticated one, it thus becomes apparent that the art has not kept pace with the demands of ever increasing circuit speed caused by faster and faster computer operating times, now measured in nanoseconds. Existing circuit card connectors can be used in the most advanced computers only at a sacrifice of eflFective operating times.

SUMMARY OF THE INVENTION It is an object of this invention to provide a circuit card connector having characteristics suitable for use with high speed computer circuitry, yet not requiring heavy structural supports.

It is another object of this invention to provide a circuit card connector of compact design that allows a high density of the connectors to be placed in an array, yet not require heavy stnictural supports.

It is a further object of this invention to provide a circuit card connector of the normally closed, spring contact type wherein the distance between active elements on the circuit card and the terminal of the spring contact is minimized.

It is another object of the invention to provide a circuit card connector of the normally closed, spring contact type wherein impedance between spring contacts positioned on opposite sides of a circuit card is reduced and wherein the distance between active elements on the circuit card and the terminal of the spring contact is minimized.

These and other related objects may be attained by employing the normally closed, zero or low insertion force, circuit card connector herein disclosed. The connector includes a housing, which may be considerably less substantial than that employed in most prior art connectors, since forces imparted to it during operation of the connector are reduced. The connector further includes spring contacts, usually of the leaf, cantilever beam type, which are supported by the housing at their terminal end. The contacts have a point of contact for a circuit card spaced from their point of support. Finally, means, usually a cam, operatively engaging the spring contact for opening the contact is provided. This means is located to apply a force substantially normal to, and substantially through and away from the point of contact of the spring contact with the circuit card. By locating the spring contact in accordance with this principle, it is possible to provide a circuit card connector having a shorter eifective distance between active elements on the circuit card and the contact terminals than has hitherto been possible. This is true because the means for opening the spring contact is not placed between the circuit card and the contact terminal, and also because it is far enough removed from the point of support of the contact in the housing to reduce stress on the housing and on the contacts at the point of support by the housing. While the connector of this invention preferably has zero insertion force (i.e., the spring contacts can be lifted completely from a circuit card for insertion or removal of a card), this is not essential to obtain all of the advantages herein disclosed for the design.

The circuit card connector design of this invention is particularly suited for the most advanced high speed computer circuitry, because the additional length imparted to computer circuitry by the connector itself is minimized. However, the desirable features of this design make it suitable for a wide variety of other applications as well.

The foregoing and other objects, features, and advantages of the invention will be apparent from the following more particular description of the preferred embodiments of the invention, as illustrated in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a side view of two arrays of the claimed connectors showing a circuit card being inserted in the arrays;

FIG. 2A is a cross section view of one of the arrays in FIG. 1 taken along the line 2A in FIG. 3 and showing details of the connector design in the closed position;

FIG. 2B is a cross section similar to that in FIG. 2A but taken along the line 2B in FIGS. 1 and 3, and showing the connector in the open position;

FIG. 3 is a perspective view of the arrays in FIG. 1, together with their associated circuit cards, showing their environment in a computer; and

FIG. 4 is a perspective view of a cam rod used in the arrays shown in FIGS. 1 and 3.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings, more particularly to FIGS. 1, 2A and 2B there is shown an example of the claimed connector, showing its essential features. Housing provides support for a pair of leaf spring contacts 12 and 12', of the cantilever beam type. The housing 10 is made of a reasonably high strength resinous material, such as glass filled polycarbonate or epoxy resin. The spring contacts are mounted in housing 10 so that their spring force tends to move them together in the direction of arrows 14 and 14, respectively, desirably until the two contact points 16 and 16' almost touch. Cams 18 and 18 are provided to bias the spring contacts away from their normally closed position against a circuit card 20, as they are shown in FIG. 2A. To open the contacts to allow insertion or removal of a circuit card, cams 18 and 18' are rotated 180 degrees to the position shown in FIG. 2B, thus lifting the contact points 16 and 16 of spring contacts 12 and 12 from the surface of circuit card 20. Opening 22 in housing 10 is provided for insertion of the circuit card 20. The contact points 16 and 16 as well as conducting lines on circuit card 20 with which it is desired to make contact both have a gold plated or clad surface to give the best contact.

The pair of spring contacts 12 and 12 is provided for contacting a card having circuits on each side. One spring contact may be employed where the card has circuitry on only one side.

The configuration of spring contacts 12 and 12' allows earns 18 and 18' to apply the force for opening them substantially normal to, and substantially through and away from, the contact points 16 and 16' of the spring contacts with circuit card 20. As shown, the spring contacts 12 and 12' have a substantially straight portion 24 extending from a support portion 26 to the contact points 16 and 16'. An arcuate portion 28 extends around from the contact points 16 and 16' and back toward the support portion 26. Cams 18 and 18 engage the arcuate portion 28 of spring contacts 12 and 12', respectively, to lift them from circuit card 20.

Terminal portion 30 on each spring contact 12 and 12' is provided for making electrical contact with other circuitry in a computer. Substantially straight portion 24, support portion 26, and terminal portion 30 of the contacts 12 and 12' all provide substantially the most direct conductive path from contact points 16 and 16' to circuitry associated with that on circuit card 20. Arcuate portion 28 is not part of the conductive path, and it does not interfere with circuit elements placed close to the edge of circuit card 20'. As a result of both of these factors, the distance between such elements and associated circuitry connected to terminal portion 30 is minimized.

In operation, a circuit card 20 is inserted in the connector in the following manner. Rods 19 and 19' (aportion of which is shown in FIG. 4), of which earns 18 and 18 form an integral part, are rotated so that the earns 18 and 18' are in the position shown in FIG. 2B. The rods 19 and 19 are supported in the array 32 by bearing surfaces 21, thus positioning the rods 19 and 19' serted in the opening 22 in housing 10 far enough so that the desired point of contact on the circuit card is opposite the contact points 16 and 16 on contact springs 12 and 12. Shafts 19 and 19' are then rotated to move the cams 18 and 18 to the position shown in FIG. 2A. In this position, the cams 18 and 18' are out of engagement with the arcuate portion 28 of each contact 12 and 12, and the contacts are in their normally closed position.

When cards having a high density of circuitry thereon, which is common in computer applications, are employed, the circuit cards must be immersed in a fluid coolant in order to keep the circuitry at suitable operating tem' peratures. The connector desing of this invention is particularly adapted for such a fluid coolant environment, as shown in FIG. 3 of the drawing. Arrays 32 of the connectors are shown embedded in a wall 34 of tank 36. The terminal portions 30 of the connectors project through the walls 34 of tank 36. The circuit cards 20 are arranged in rows in the tank. The tank contains a suitable liquid coolant 38, such as a high-purity Freon coolant or the like. Cover 40 of the tank 36 has a heat exchanger 42 mounted thereon, which serves to conduct heat from the tank 36 during operation.

The operating temperatures of the circuit cards 20 are high enough to cause nucleate boiling in the fluid coolant 38. Such boiling is a very efficient way of transmitting heat from the cards 20 to the heat exchanger 42, and thence out of the system.

At the operating speeds now contemplated for advanced computers, it was determined that a maximum effective length between the contact points 16 and 16 of the contacts 12 and 12' on circuit card 20 and the terminal portion 30 of the contacts of no more than 800 mils could be tolerated without a sacrifice in machine operating time. With the design as disclosed above, it was possible to obtain such an effective length of only 500 mils, well below the required limit. No previous circuit card connector design was found capable of meeting this limit in the above described environment. The connector design of this invention is capable of imparting a contact force of between and 500 grams between the point of contact on the spring contact and the circuit card. This amount of contact force is sufficient for a gold-on-gold connector in a controlled atmosphere, such as the highpurity fluid coolant employed in tank 30. If other contact materials are employed, or if it is desired to use the connector in a non-controlled atmosphere, more contact force will be required. If additional contact force cannot be obtained from the spring force of the contacts 12 alone, a biasing member imparting force on the contact springs to cause additional contact force to be exerted against the circuit card 24 may be employed. Such biasing members are desirably located at some point between the point of support for the spring contacts 12 and 12' and their points of contact 16 and 16'.

It should now be apparent that an improved circuit card connector suitable for high speed computer operating times, which may be used in a high density in an array without requiring heavy structural supports, has been provided. The disclosed circuit card connector enables the distance between active elements on a circuit card and the terminal of the connector to be minimized. Finally, the spacing between opposing contacts of the connector is reduced, thus reducing objectionable noise in output caused by impedance. Most significantly, these objects have been attained in a connector that is easier and cheaper to fabricate than prior art designs not capable of attaining the stated objects.

While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.

What is claimed is:

1. A normally closed circuit card connector comprismg:

(A) A housing;

(B) a leaf type spring contact fixedly supported by the housing at one end of the spring contact and having a point of contact for a circuit card spaced from the point of support; and

(C) means operatively engaging the spring contact at a point along the spring contact at least as remote from the point of support as the point of contact for the circuit card for applying a force along an axis substantially normal to a surface of the circuit card, and substantially through and away from, the point of contact of the spring contact.

2. An array of the circuit card connectors of claim 1 for contacting a plurality of points on a circuit card.

3. A circuit card connector as in claim 1 having zero insertion force wherein the spring contact is of the cantilever beam type and has a substantially straight portion extending from the support portion on the housing to the point of contact for a circuit card, and an additional portion extending from the point of contact, and wherein the means for applying a force to the spring contact engages the additional portion.

4. The circuit card connector of claim 3 wherein the additional portion of the spring contact is arcuate and extends around and back from the point of contact toward the point of support and wherein the means for applying a force to the spring contact is a cam placed to be rotated against the arcuate additional portion of the spring contact to lift the spring contact from the circuit card.

5. A circuit card connector as in claim 1 having a pair of spring contacts of the cantilever beam type for contacting opposite sides of a circuit card and a means operatively engaging each spring contact at a point along the spring contacts at least as remote from the point of support as the point of contact for the circuit card for applying a force along an axis substantially normal to a surface of the circuit card, and substantially through and away from, the point of contact of each spring contact.

6. An array of the circuit card connectors of claim 5 for contacting a plurality of points on a circuit card.

7. In a normally closed circuit card connector having a spring contact with a point of support and a point of contact for the circuit card spaced from the point of support, the improvement comprising means operatively engaging the spring contact at a point along the spring contact at least as remote from the point of support as the point of contact for the circuit card for applying a force along an axis substantially normal to a surface of the circuit card, and substantially through and away from, the point of contact of the spring contact with the circuit card.

8. The connector of claim 7 wherein the means for applying a force to the spring contact is a cam.

References Cited UNITED STATES PATENTS 2,857,577 10/1958 Vanderpool 33917 3,022,481 2/ 1962 Stepoway 339- 3,188,598 6/1965 Pferd 33917 MARVIN A. CHAMPION, Primary Examiner J. H. MCGLYNN, Assistant Examiner 

